A result of the continuing evolution in technologies for cellular telephony is that it is possible for several different technologies to coexist and overlap to varying degrees within a given subscriber market. Because these different technologies and the networks based thereon have different characteristics and operational considerations, certain incompatibilities may arise between the networks that limit the abilities of Service Providers to offer associated services to the subscribers.
As an illustration of the above concern, consider, as a non-limiting example shown conceptually in FIG. 1, the case of a Subscriber who initially obtained two cellular telephones from a Service Provider operating a single-protocol TDMA (Time Division Multiple Access) network 101. A telephone 103 set up for hands-free operation is installed in the Subscriber's car, whereas another telephone 105 is a smaller and more compact unit which the Subscriber carries on his person. Both telephones 103 and 105 are configured within TDMA network 101 to have a common telephone number 107, wherein telephone 105 is designated as the “primary” telephone. An incoming call 111 to common number 107 is thus routed first to telephone 105. If, however, telephone 105 is not reachable, is busy, or is not answered, incoming call 111 is then automatically routed to telephone 103, which is designated as the “secondary telephone”. In this fashion, the Subscriber receives the call on the appropriate telephone regardless of his location. In addition, both telephone 103 and telephone 105 identify themselves in the same way to network 101, so the Subscriber can utilize them in a completely interchangeable fashion to access so the Subscriber can utilize them in a completely interchangeable fashion to access one or more common Subscriber services 109 (such as voice-mail). The term “common Subscriber service” herein denotes ancillary services (including, but not limited to voice mail notifications, e-mail, Internet access, caller ID, unified billing, voice-activated dialing, and virtual private network) which are available in substantially identical form via both telephones. As far network 101 is concerned, both telephone 103 and telephone 105 are physically distinct at the device level, so that primary telephone 105 may be readily distinguished from secondary telephone 103 for the purpose of making cellular connections. At the service level, however, network 101 can treat telephone 103 as substantially identical to telephone 105, because they have the same CLI (Calling Line Identity), so that from the Subscriber's viewpoint, it makes absolutely no difference whether he uses telephone 103 or telephone 105 to access one or more common Subscriber services 109, which are associated with common telephone number 107. Equivalence of this kind (where telephone 103 can be used interchangeably with telephone 105 both to send and receive calls associated with the same telephone number as origination and destination, respectively), is herein denoted by the term “substantially identical”. The term “substantially identical” is also used herein with reference to accessing common Subscriber services, denoting that the Subscriber interface associated with each telephone appears substantially the same to the Subscriber. As a non-limiting example of this, the procedures, codes, or keystrokes a Subscriber would employ to access his voice-mail box would be substantially the same regardless of which telephone he used to perform the access.
Because both telephone 103 and telephone 105 communicate over the same TDMA network 101, the above arrangement, which is of benefit to the Subscriber, is relatively straightforward to implement, and is known in the prior art.
It is noted that there are operational differences between the case whereby two telephones share a common telephone number and the case of “call forwarding”, whereby a telephone call to a first telephone having a first telephone number is redirected to a second telephone having a second (and different) telephone number. Superficially, in the call forwarding case, it could appear to the caller as if the second telephone, which has received a call intended for the first telephone, would have the same telephone number as the first telephone. In call-forwarding, however, only incoming telephone calls exhibit this property. An outgoing call made from the second telephone would be associated with the second telephone number, not the telephone number of the first telephone. From this standpoint, call forwarding per se does not produce a situation whereby both telephones truly share a common telephone number. In addition, the second telephone will still respond to calls directed to the second telephone number. Moreover, call forwarding operates either in strict sequence (initially paging the first telephone and thereafter paging the second telephone) or in an override mode (where only the second telephone is paged and the first telephone is bypassed). Sharing a common telephone number, on the other hand, can also operate in a simultaneous paging mode whereby both telephones are paged at the same time. Furthermore, call forwarding is usually implemented on a case-by-case basis, and often requires the interaction and attention of the Subscriber (to initiate and cancel call forwarding). Call-forwarding techniques can be used in combination with other techniques to effect the sharing of a common telephone number between two telephones, but additional capabilities are needed to provide all the relevant characteristics of true sharing as opposed to mere call-forwarding.]
To continue with the above illustration, suppose that, at a later time, the Service Provider begins operating a single-protocol GSM (Global System for Mobile Communications) network in addition to the original single-protocol TDMA network, which continues in operation to support the existing TDMA telephones. Although both TDMA and the GSM communication networks are considered to be at the same “second-generation” level, there may be various reasons for the Service Provider to desire to expand service into the GSM area. For example, the advanced GPRS (General Packet Radio Service) for higher-speed data communications is layered on GSM protocols. In addition, GSM is a de facto standard in the European and Asian markets, and Service Providers in other regions may wish to migrate in that direction as well.
FIG. 2 conceptually illustrates what happens when the Subscriber of this example wishes to obtain a GSM telephone to replace telephone 105 (FIG. 1), which he carries on his person. TDMA telephone 103 installed in his car, however, is still perfectly suitable to the Subscriber, and to avoid the cost and inconvenience of having to obtain and install a new telephone in his car, the Subscriber also wishes to retain TDMA telephone 103, which is already installed therein. The Subscriber thus obtains a single-protocol GSM telephone 205.
Unfortunately for the Subscriber, however, GSM telephone 205, which he now carries on his person, communicates over a network 201, which is distinct from network 101 within which communicates telephone 103. Even though network 101 and network 201 are both operated by the same Service Provider, they are not compatible with one another because they are both single-protocol networks based on different protocols. Two single-protocol networks which operate according to different protocols are herein denoted as “incompatible networks”, in contrast to “compatible networks”, which operate according to substantially identical protocols. The result is that the Subscriber cannot have the same arrangement he previously had, where telephone 103 and telephone 105 (FIG. 1) both had telephone number 107 and where he could access one or more common Subscriber services 109 in a substantially identical fashion from either telephone 103 or telephone 105. Instead, as shown in FIG. 2, telephone 205 has a distinct telephone number 207 (052499035) and Subscriber services 209. Secondary telephone 103 has a telephone number 208 (064120123).
Although it may be possible, using prior art techniques, for the Service Provider to automatically perform a “call-forwarding” operation to re-route a call 211 originally directed to 052499035 (telephone number 207) via a call forward 213 to 064120123 (telephone number 208), it is not possible for telephone 103 and telephone 205 to be treated the same at the service level, because they communicate over separate and distinct networks. Neither is it possible for telephone 103 and telephone 205 to share a common telephone number, because the arrangement shown in FIG. 1, which shares telephone number 107 between telephone 103 and telephone 105, is not applicable to separate networks. This limitation further restricts the Subscriber from accessing the same (common) Subscriber services (such as his voice-mail box) from both telephones. From telephone 103 he can access Subscriber services 109 but not Subscriber services 209, whereas from telephone 205 he can access Subscriber services 209 but not Subscriber services 109.
In addition to the non-limiting example given above, there are other reasons to desire the capability of sharing a common telephone number and common Subscriber services between two telephones communicating over distinct networks. As noted previously, the GSM technology is a de facto standard in European and Asian markets, and Service Providers in other regions may wish to migrate their subscriber base to GSM. This can prove difficult in large markets, such as the North American market, where a substantial infrastructure investment is needed to duplicate the coverage of the existing TDMA network in a parallel GSM network. Accordingly, a Service Provider might prefer to introduce the new GSM network gradually into operation. Unfortunately, however, this means that the GSM network may be put into operation without full coverage of the subscriber area. In order to obtain full coverage, therefore, it may therefore be necessary for the Subscriber to continue to utilize an existing TDMA telephone in addition to a new GSM telephone (or, alternatively, a single telephone that can communicate with both a TDMA network and a GSM network). Thus, there are other cases where a Subscriber may have two different telephones communicating over two different networks, where the same telephone number may be desired for both telephones, and access to the same (common) Subscriber services may be desired for both telephones as well.
Not only do the limitations of the prior art in handling the situations described above create a disadvantage to the Subscriber, but from a more general marketing standpoint it is noted that the Subscriber is not expected to be aware of the technical aspects of the different cellular telephone technologies and networks based thereon. To the Subscriber, the differences between one cellular telephone and another involve issues such as size, cost, and other tangible consumer features. The subscriber market is thus not to be expected to be understanding of the technical limitations created by incompatibilities between telephones in different networks. As a consequence, any limitations in technical compatibility between different cellular networks can result in marketing disadvantages to the Service Provider as well as inconvenience to the Subscribers.
As noted previously, the examples presented above are provided solely to illustrate the nature of consequences resulting from the technical incompatibilities of different networks that are in simultaneous use, and are not intended to imply that the limitations of current systems affect only such cases. In particular, the above examples of prior art limitations can be extended to any combination of several telephones installed in automobiles and carried on one's person (such as two different telephones installed in two different automobiles, two different telephones carried on one's person, and so forth), and can also be extended to a single telephone capable of communicating over several different networks. Furthermore, although the illustrations and examples presented herein are expressed in terms of TDMA/CDMA (using IS-41 protocol) and GSM networks, it is understood that the technical limitations of existing cellular communications systems are not restricted to such networks, but are encountered in cellular networks of all types. Moreover, the limitations of the prior art affect not only cellular telephones, but mobile stations in general, including, but not limited to cellular telephones and wireless data terminals.
Roaming and the “Interworking Interoperability Function” (IIF), and GAIT
When a Subscriber mobile station is physically located outside the region supported by the Subscriber's Service Provider, a “roaming” condition exists, whereby the mobile station must be registered with the HLR (Home Location Register) of a network other than the original network with which the mobile station is associated. Normally, a mobile station is capable of roaming only within a compatible network. That is, a TDMA telephone can roam only within a TDMA network; a GSM telephone can roam only within a GSM network; and so on. However, due to the increased geographical mobility of the subsciber base, there are many mobile subscribers who would like to use their mobile telephones without such a restriction. To achieve such an advantage, the GAIT (GSM/ANSI-41 Interoperability Team) protocol has been developed to implement an Interworking Interoperability Function (IIF), whereby a multi-protocol mobile telephone (such as the GAIT-compliant Nokia 6340 telephone) can roam in both TDMA and GSM networks, provided that these networks are enhanced to support the GAIT protocol, by the addition of special equipment. Effectively, GAIT allows constructing a multi-protocol network from a single-protocol TDMA network and a single-protocol GSM network, such that the TDMA network and the GSM network can share information about mobile subscribers, wherein the subscribers obtain access to most services when using either type of protocol with a GAIT-compliant multi-protocol telephone. The GAIT protocol is covered in a number of detailed documents which are part of the published GSM/ANSI-136 Interoperability Team Specification.
Although GAIT provides a solution whereby a mobile subscriber can roam in both TDMA and GSM networks, there are several practical and marketing disadvantages to this approach: To begin with, the Service Provider must make a substantial investment in the network infrastructure. In addition, the Subscriber must purchase a special GAIT-compliant multi-protocol telephone (capable of operating over both TDMA networks and GSM networks). Such multi-protocol telephones are typically much more expensive than regular single-protocol telephones (which function either over a TDMA network or over a GSM network, but not over both). In addition, there is much less variety available among GAIT-compliant multi-protocol telephones than there is among single-protocol telephones. For example, a Subscriber has many different models of inexpensive single-protocol GSM telephones from which to choose, some of which offer special features and benefits which may be of value to the Subscriber. In contrast, there are relatively few GAIT-compliant multi-protocol telephones available. With GAIT, therefore, the Subscriber has to pay much more for a telephone, but has much less choice. Moreover, the future of multi-protocol networks is not clear: it is likely that the importance of “interoperability” between different network technologies will decline in the future as wireless communication standards evolve and merge into a single unified global network. Thus, the substantial added investment in GAIT technology (for both the Subscriber and the Service Provider alike) is liable to realize a return only over a relatively short term. Consequently, many Service Providers are reluctant to make the large investment in GAIT-compliant technology. Furthermore, even though GAIT provides for so-called “seamless” roaming, the precise nature of the Subscriber Services may still vary from one network to another, and the Subscriber may experience some discontinuities in such Subscriber Services when using GAIT-compliant multi-protocol networks and telephones. As a result from a marketing and economic standpoint, GAIT may not be a completely satisfactory long-term solution to the challenges encountered in frequent and prolonged Subscriber roaming.
There are a number of other prior-art technologies which also relate to various aspects of the issues of inter-network compatibility and unity of services. Some of these are addressed below:
For example, United States Patent application 20020012351 by Sofer, et al. (hereinafter referred to as “Sofer”), discloses a method and system for providing services to roaming subscribers of mobile telephone networks which are applicable to different network protocols. However, Sofer does not disclose means by which different wireless technologies may be integrated, nor does it cover the use of different telephones which share, or are intended to share, a common telephone number.
As another example, Ericsson, in addition to providing a GAIT-compliant “Mobility Gateway”, also offers a “Fixed Mobile Convergence” (FMC) solution in which a single telephone number may be used for both a fixed (land-line based) telephone and a mobile telephone, and in which certain Subscriber Services, such as voice mail and billing, may be integrated. The Ericsson FMC solution, however, differs from the background of the present invention in that one of the essential telephone systems involved is not a mobile network.
Despite the broad interest in inter-network compatibility and unity of services, there is no present technology capable of combining both inter-network compatibility and unity of services along with telephone number transparency in a cost-effective manner and easy manner based on existing single-protocol equipment.
There is thus a need for, and it would be highly advantageous to have, a method and system for cost-effectively providing multi-protocol network access to provide telephone number transparency and complete unity of common Subscriber services to the Subscriber. It would furthermore be advantageous to provide such a capability which the Subscriber may utilize without having to obtain a multi-protocol telephone, and which likewise does not require the Service Provider to invest in extensive modifications to the networks. These goals are met by the present invention.